Abstract

Background

It has been demonstrated that extracellular mRNA can be detected in the circulation.
Our hypothesis was that circulating miRNAs are also present and differentially expressed
in the serum of breast cancer patients compared to controls.

Findings

We measured miRNA in the serum of samples with and without the addition of miRNA prior
to analysis. To test our RNA extraction efficiency, we spiked-in serial dilutions
of single-strand C elegens miR-39 (cel-miR-39) and human miR-145 (has-miR-145) into
goat serum and a 10 year old human serum specimen. We next analyzed miR-16, -145,
and -155 in archived serum specimens from 21 participants, 13 of whom did and 8 of
whom did not have breast cancer. We were able to detect the miRNAs from all the serum
samples to which the miRNAs had been added. We were also able to detect endogenous
miR-16, -145, and -155 in all serum samples. While the expression of all three miRNAs
was similar in samples from healthy women compared to those with breast cancer, women
with progesterone receptor (PR, p = 0.016) positive tumors had higher miR-155 expression
than tumors that were negative for these receptors.

Conclusion

1) RNA species can be detected in archived serum; 2) miR-155 may be differentially
expressed in the serum of women with hormone sensitive compared to women with hormone
insensitive breast cancer. Screening serum for miRNAs that predict the presence of
breast cancer is feasible, and may be useful for breast cancer detection.